ηmax-Charging Strategy for Lithium-Ion Batteries in V2G Applications

The design of charging strategies for lithium-ion (Li-ion) batteries depends on the application. In electric vehicle applications, high charging speed and long battery life are essential requirements. However, with the advent of vehicle-to-grid (V2G) and potential remuneration for electric grid support, maximum user profit could gain increasing interest through efficient operation that also optimizes battery health. Conventional constant-current constant voltage (CCCV) and constant-power constant-voltage (CPCV) charging strategies do not include the optimum efficiency of the battery and charging stations. In this paper, a charging strategy is introduced aiming at maximizing the instantaneous efficiency (ηmax of the Li-ion battery and the charging station which minimizes the energy waste. For this purpose, 18650 Li-ion cells and a dual-active-bridge (DAB) converter are considered in the simulations and experimental validations. The results show that the ηmax -charging strategy outperforms conventional CCCV and CPCV charging strategies in terms of efficiency and material-lifetime compatibility.